Optical imaging system

ABSTRACT

An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens having a negative refractive power, a fifth lens having a negative refractive power, a sixth lens, and a seventh lens having a positive refractive power. The first lens to seventh lens are sequentially disposed in a direction from an object side toward an imaging plane.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/594,686 filed on May 15, 2017, which claims the benefit under 35U.S.C. § 119(a) of Korean Patent Application Nos. 10-2016-0117304 filedon Sep. 12, 2016, and 10-2016-0159277 filed on Nov. 28, 2016, in theKorean Intellectual Property Office, the entire disclosures of which areincorporated herein by reference for all purposes.

BACKGROUND 1. Field

The following description relates to a telescopic optical imaging systemincluding seven lenses.

2. Description of Related Art

Telescopic optical imaging systems capable of capturing images ofdistant objects may be significantly large. In detail, in terms oftelescopic optical imaging systems, the ratio (TL/f) of the overalllength TL of a telescopic optical imaging system to the overall focallength f may be greater than or equal to 1. Thus, it may be difficult tomount telescopic optical imaging systems in small electronic devices,such as portable terminals.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, an optical imaging system includes a first lens,a second lens, a third lens, a fourth lens having a negative refractivepower, a fifth lens having a negative refractive power, a sixth lens,and a seventh lens having a positive refractive power.

The first lens of the optical imaging system may have a conveximage-side surface along an optical axis. The second lens of the opticalimaging system can have a convex object-side surface along an opticalaxis. The third lens of the optical imaging system may have a convexobject-side surface along an optical axis.

The fourth lens of the optical imaging system may have a meniscus formin which one side surface is concave along an optical axis, and theother side surface is convex along the optical axis. The fifth lens ofthe optical imaging system can have a concave object-side surface alongan optical axis. The sixth lens of the optical imaging system may haveopposing concave surfaces along an optical axis. The seventh lens of theoptical imaging system can have opposing convex surfaces along anoptical axis.

In another general aspect, an optical imaging system includes first toseventh lenses, sequentially disposed from an object side to an imagingplane, wherein a ratio (TL/f) of a distance TL from an object-sidesurface of the first lens to an imaging plane to an overall focal lengthf is less than or equal to 1.0.

The optical imaging system may satisfy the expression BFL/f<0.15, whereBFL represents a distance from an image-side surface of the seventh lensto an imaging plane. The optical imaging system can satisfy theexpression 0.1<f/(IMG HT)<2.5, where IMG HT is a half diagonal length ofthe imaging plane. The optical imaging system may satisfy the expression1.5<Nd7<1.7, where Nd7 represents a refractive index of the seventhlens.

The optical imaging system may satisfy the expression −45<f5/f<45, wheref5 represents a focal length of a fifth lens. The optical imaging systemcan satisfy the expression 2.0<f/EPD<2.8, where EPD represents adiameter of an entrance pupil. The second lens, fourth lens, and sixthlens of the optical imaging system may each have a negative refractivepower. The sixth lens of the optical imaging system can have a concaveobject-side surface along an optical axis.

In another general aspect, an optical imaging system includes a firstlens having a positive refractive power and a convex object-side surfacealong an optical axis, a second lens having a concave image-side surfacealong the optical axis, a third lens, a fourth lens, a fifth lens, asixth lens, and a seventh lens. The first lens to seventh lens aresequentially disposed from an object side to an imaging plane. One orboth surfaces of each of the first to seventh lenses are aspherical.

The object-side surface of the first lens of the optical imaging systemmay include a most convex point of the system. The image-side surface ofthe second lens of the optical imaging system can include a most concavepoint of the system. The third lens of the optical imaging system mayhave a meniscus form in which one side surface is concave and the otherside surface is convex. The fifth lens of the optical imaging system canhave a convex image-side surface. The seventh lens of the opticalimaging system may be bi-convex with a positive refractive power or maybe bi-concave with a negative refractive power.

In another general aspect, an optical imaging system includes a firstlens to a seventh lens. The first lens and the seventh lens each have apositive refractive power, a convex object-side surface along an opticalaxis and a convex image-side surface along the optical axis. The firstlens to seventh lens are sequentially disposed from an object side to animaging plane.

The object-side surface of the first lens of the optical imaging systemmay include a most convex point of the optical imaging system. Thesecond lens to sixth lens of the optical imaging system can each have anegative refractive power. The image-side surface of the second lens ofthe optical imaging system may be concave and may have a most concavepoint of the optical imaging system.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an optical imaging system according to a firstexample.

FIG. 2 is a set of graphs illustrating aberration curves of the opticalimaging system illustrated in FIG. 1.

FIG. 3 is a table listing aspherical characteristics of the opticalimaging system illustrated in FIG. 1.

FIG. 4 is a diagram of an optical imaging system according to a secondexample.

FIG. 5 is a set of graphs illustrating aberration curves of the opticalimaging system illustrated in FIG. 4.

FIG. 6 is a table listing aspherical characteristics of the opticalimaging system illustrated in FIG. 4.

FIG. 7 is a diagram of an optical imaging system according to a thirdexample.

FIG. 8 is a set of graphs illustrating aberration curves of the opticalimaging system illustrated in FIG. 7.

FIG. 9 is a table listing aspherical characteristics of the opticalimaging system illustrated in FIG. 7.

FIG. 10 is a diagram of an optical imaging system according to a fourthexample.

FIG. 11 is a set of graphs illustrating aberration curves of the opticalimaging system illustrated in FIG. 10.

FIG. 12 is a table listing aspherical characteristics of the opticalimaging system illustrated in FIG. 10.

FIG. 13 is a rear view of a portable terminal including an opticalimaging system mounted therein according to an example.

FIG. 14 is a cross-sectional view of the portable terminal illustratedin FIG. 13.

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements, where applicable. The drawings maynot be to scale, and the relative size, proportions, and depiction ofelements in the drawings may be exaggerated for clarity, illustration,or convenience.

DETAILED DESCRIPTION

Hereinafter, examples will be described as follows with reference to theattached drawings. Examples provide an optical imaging system capable ofcapturing images of distant objects and being mounted in a smallterminal. The disclosure may, however, be exemplified in many differentforms and should not be construed as being limited to the specificembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the disclosure after an understanding of thisapplication.

Throughout the specification, it will be understood that when anelement, such as a layer, region or wafer (substrate), is referred to asbeing “on,” “connected to,” or “coupled to” another element, it can bedirectly “on,” “connected to,” or “coupled to” the other element orother elements intervening therebetween may be present. In contrast,when an element is referred to as being “directly on,” “directlyconnected to,” or “directly coupled to” another element, there may be noelements or layers intervening therebetween. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Although terms such as “first,” “second,” and “third” may be used hereinto describe various components, regions, or sections, these components,regions, or sections are not to be limited by these terms. Rather, theseterms are only used to distinguish one component, region, or sectionfrom another component, region, or section. Thus, a first component,region, or section referred to in examples described herein may also bereferred to as a second component, region, or section without departingfrom the teachings of the examples.

The articles “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. The terms“comprises,” “includes,” and “has” specify the presence of statedfeatures, numbers, operations, members, elements, and/or combinationsthereof, but do not preclude the presence or addition of one or moreother features, numbers, operations, members, elements, and/orcombinations thereof.

Due to manufacturing techniques and/or tolerances, variations of theshapes shown in the drawings may occur. Thus, the examples describedherein are not limited to the specific shapes shown in the drawings, butinclude changes in shape that occur during manufacturing.

The features of the examples described herein may be combined in variousways as will be apparent after an understanding of the disclosure ofthis application. Further, although the examples described herein have avariety of configurations, other configurations are possible as will beapparent after an understanding of the disclosure of this application.

According to an example, a first lens refers to a lens closest to anobject or a subject of which an image is captured. A seventh lens refersto a lens closest to an imaging plane or an image sensor. In the presentspecification, an entirety of a radius of curvature, a thickness, adistance from an object-side surface of a first lens to an imaging plane(TL), a half diagonal length of the imaging plane (IMG HT), and a focallength of a lens are indicated in millimeters (mm). A person skilled inthe relevant art will appreciate that other units of measurement may beused. Further, in embodiments, all radii of curvature, thicknesses, OALs(optical axis distances from the first surface of the first lens to theimage sensor), a distance on the optical axis between the stop and theimage sensor (SLs), image heights (IMGHs) (image heights), and backfocus lengths (BFLs) of the lenses, an overall focal length of anoptical system, and a focal length of each lens are indicated inmillimeters (mm). Further, thicknesses of lenses, gaps between thelenses, OALs, TLs, SLs are distances measured based on an optical axisof the lenses.

In a description of a form of a lens, a surface of a lens being convexmeans that an optical axis portion of a corresponding surface is convex,while a surface of a lens being concave means that an optical axisportion of a corresponding surface is concave. Therefore, in aconfiguration in which a surface of a lens is described as being convex,an edge portion of the lens may be concave. In a manner the same as thecase described above, even in a configuration in which a surface of alens is described as being concave, an edge portion of the lens may beconvex. In other words, a paraxial region of a lens may be convex, whilethe remaining portion of the lens outside the paraxial region is eitherconvex, concave, or flat. Further, a paraxial region of a lens may beconcave, while the remaining portion of the lens outside the paraxialregion is either convex, concave, or flat. In addition, in anembodiment, thicknesses and radii of curvatures of lenses are measuredin relation to optical axes of the corresponding lenses.

In accordance with illustrative examples, the embodiments described ofthe optical system include seven lenses with a refractive power.However, the number of lenses in the optical system may vary, forexample, between two to seven lenses, while achieving the variousresults and benefits described below. Also, although each lens isdescribed with a particular refractive power, a different refractivepower for at least one of the lenses may be used to achieve the intendedresult.

An optical imaging system includes seven lenses. For example, theoptical imaging system may include the first lens, a second lens, athird lens, a fourth lens, a fifth lens, a sixth lens, and the seventhlens, sequentially disposed from an object side.

The first lens has a refractive power. For example, the first lens has apositive refractive power. The first lens has at least one convexsurface. In an embodiment, the first lens has a convex object-sidesurface.

The first lens has an aspherical surface. For example, both surfaces ofthe first lens are aspherical. The first lens may be formed using amaterial having a relatively high degree of light transmittance andexcellent workability. In an example, the first lens is formed using aplastic material. However, a material of the first lens is not limitedto being a plastic material. In another example, the first lens may beformed using a glass material. The first lens has a relatively lowrefractive index. For example, a refractive index of the first lens isless than 1.6.

The second lens has a refractive power. For example, the second lens hasa negative refractive power. The second lens has a convex surface. In anembodiment, the second lens may have a convex object-side surface.

The second lens has an aspherical surface. For example, the second lenshas an aspherical object-side surface. The second lens may be formedusing a material having a relatively high degree of light transmittanceand excellent workability. In an example, the second lens is formedusing a plastic material. However, a material of the second lens is notlimited to being plastic. In another example, the second lens may beformed using a glass material. The second lens has a reflective indexhigher than that of the first lens. For example, a refractive index ofthe second lens is greater than or equal to 1.65.

The third lens has a refractive power. For example, the third lens mayhave a positive or a negative refractive power. The third lens has ameniscus form in which one surface is concave, and the other surface isconvex. In embodiments, the third lens has a form in which anobject-side surface is convex and an image-side surface is concave, orhas a form in which the object-side surface is concave and theimage-side surface is convex.

The third lens has an aspherical surface. For example, the third lenshas an aspherical image-side surface. The third lens may be formed usinga material having a relatively high degree of light transmittance andexcellent workability. In an example, the third lens is formed using aplastic material. However, a material of the third lens is not limitedto being plastic. In another example, the third lens may be formed usinga glass material. The third lens has a refractive index substantiallysimilar to that of the first lens. In detail, the refractive index ofthe third lens is less than 1.6.

The fourth lens has a refractive power. For example, the fourth lens hasa negative refractive power. The fourth lens has the meniscus form inwhich one surface is concave and the other surface is convex. Inembodiments, the fourth lens has a form in which an object-side surfaceis convex and an image-side surface is concave, or has a form in whichthe object-side surface is concave and the image-side surface is convex.

The fourth lens has an aspherical surface. For example, both surfaces ofthe fourth lens are aspherical. The fourth lens may be formed using amaterial having a relatively high degree of light transmittance andexcellent workability. In an example, the fourth lens is formed using aplastic material. However, a material of the fourth lens is not limitedto being plastic. In another example, the fourth lens may be formedusing a glass material. The fourth lens has a refractive index greaterthan or equal to that of the first lens.

The fifth lens has a refractive power. For example, the fifth lens mayhave a positive or a negative refractive power. The fifth lens has aconcave surface. In an embodiment, the fifth lens has a concaveobject-side surface.

The fifth lens has an aspherical surface. For example, both surfaces ofthe fifth lens are aspherical. The fifth lens may be formed using amaterial having a relatively high degree of light transmittance andexcellent workability. In an example, the fifth lens is formed using aplastic material. However, a material of the fifth lens is not limitedto being plastic. In another example, the fifth lens may be formed usinga glass material. The fifth lens has a refractive index higher than thatof the first lens. In an embodiment, the refractive index of the fifthlens is greater than or equal to 1.6.

The sixth lens has a refractive power. For example, the sixth lens has anegative refractive power. The sixth lens may have a concave surface.For example, the sixth lens has a concave object-side surface. The sixthlens may have an inflection point. In an embodiment, the sixth lensincludes one or more inflection points formed on opposing surfaces.

The sixth lens has an aspherical surface. For example, both surfaces ofthe sixth lens are aspherical. The sixth lens may be formed using amaterial having a relatively high degree of light transmittance andexcellent workability. In an example, the sixth lens is formed using aplastic material. However, a material of the sixth lens is not limitedto being plastic. In another example, the sixth lens may be formed usinga glass material. The sixth lens has a refractive index substantiallysimilar to that of the first lens. In an embodiment, the refractiveindex of the sixth lens is less than 1.6.

The seventh lens has a refractive power. For example, the seventh lenshas a positive or a negative refractive power. The seventh lens may haveopposing surfaces formed substantially in a symmetrical manner. Forexample, the seventh lens may have a convex object-side surface oropposing concave surfaces. The seventh lens may include an inflectionpoint. In an embodiment, the seventh lens includes one or moreinflection points formed on opposing surfaces.

The seventh lens may have an aspherical surface. For example, bothsurfaces of the seventh lens are aspherical. The seventh lens may beformed using a material having a relatively high degree of lighttransmittance and excellent workability. In an example, the seventh lensis formed using a plastic material. However, a material of the seventhlens is not limited to being plastic. In another example, the seventhlens may be formed using a glass material. The seventh lens has arefractive index lower than that of the first lens. In an embodiment,the refractive index of the seventh lens is less than 1.53.

Aspherical surfaces of the first to seventh lenses may be expressedusing Formula 1.

$\begin{matrix}{Z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {Ar}^{4} + {Br}^{6} + {Cr}^{8} + {Dr}^{10} + {Er}^{12} + {Fr}^{14} + {Gr}^{16} + {Hr}^{18} + {Jr}^{20}}} & {{Formula}\mspace{14mu} 1}\end{matrix}$

In Formula 1, c represents an inverse of a radius of curvature of alens, k represents a conic constant, r represents a distance from acertain point on an aspherical surface of the lens to an optical axis, Ato J represent aspherical constants, and Z (or SAG) represents adistance between the certain point on the aspherical surface of the lensat the distance r and a tangential plane meeting the apex of theaspherical surface of the lens.

The optical imaging system further includes a filter, an image sensor,and a stop. The filter is disposed between the seventh lens and theimage sensor. The filter may block a portion of wavelengths of visiblelight, in order to generate a clear image. For example, the filterblocks light of an infrared wavelength.

The image sensor forms an imaging plane. For example, a surface of theimage sensor may form the imaging plane. The stop is disposed to adjustan amount of light incident on a lens. In detail, the stop may beinterposed between the second lens and the third lens or between thethird lens and the fourth lens.

The optical imaging system satisfies the following ConditionalEquations:

0.7<TL/f<1.0  [Conditional Equation 1]

BFL/f<0.15  [Conditional Equation 2]

0.1<f/(IMG HT)<2.5  [Conditional Equation 3]

1.5<Nd7<1.7  [Conditional Equation 4]

−45<f5/f<45  [Conditional Equation 5]

2.0<f/EPD<2.8  [Conditional Equation 6]

In the Conditional Equations, TL represents a distance from theobject-side surface of the first lens to an imaging plane, f representsan overall focal length of the optical imaging system, BFL represents adistance from an image-side surface of the seventh lens to an imagingplane, and IMG HT represents a half diagonal length of the imagingplane. Nd7 represents a refractive index of the seventh lens, f5represents a focal length of the fifth lens, and EPD represents adiameter of an entrance pupil.

Conditional Equation 1 is provided for the miniaturization of theoptical imaging system. In detail, in cases in which the optical imagingsystem is beyond an upper limit value of Conditional Equation 1, it maybe difficult to miniaturize the optical imaging system, so that it maybe difficult to mount the optical imaging system in a portable terminal.In cases in which the optical imaging system is below a lower limitvalue of Conditional Equation 1, it may be difficult to manufacture theoptical imaging system.

Conditional Equation 2 is provided for mounting the optical imagingsystem in a portable terminal. In detail, ease of manufacturing theoptical imaging system beyond an upper limit value of ConditionalEquation 2 is facilitated, but resolution of the optical imaging systemmay be relatively low.

Conditional Equation 3 is a parametric ratio for maintaining telescopiccharacteristics and relatively high resolution. In detail, the opticalimaging system beyond an upper limit of Conditional Equation 3 may haveexcellent telescopic characteristics, but it may be difficult toimplement relatively high resolution. The optical imaging system below alower limit of Conditional Equation 3 may implement a relatively wideangle of view, but may have relatively poor telescopic characteristics.

Conditional Equation 4 is provided as a parameter of the seventh lensfor a high-resolution optical imaging system. In detail, because theseventh lens satisfying a numerical range of Conditional Equation 4 hasa relatively low Abbe number (less than or equal to 26), ease ofcorrection of astigmatism, longitudinal chromatic aberrations, andchromatic aberrations of magnification is facilitated.

Conditional Equation 5 is provided as a parametric ratio of the fifthlens for a high-resolution optical imaging system. In detail, in casesin which the fifth lens is outside of a numerical range of ConditionalEquation 5, the fifth lens may increase aberrations, so that it may bedifficult to provide a high-resolution optical system. ConditionalEquation 6 is provided as a numerical range of an F number for ahigh-resolution optical imaging system.

In the optical imaging system, a lens having a relatively high degree ofpositive refractive power may be disposed to be adjacent to an object.In detail, the first lens in the optical imaging system has the highestdegree of positive refractive power. In the optical imaging system, alens having a relatively high degree of negative refractive power may bedisposed to be substantially adjacent to the imaging plane. Inembodiments, the sixth lens has the highest degree of negativerefractive power. However, in cases in which the seventh lens has anegative refractive power, the second lens may have the highest degreeof negative refractive power.

In the optical imaging system, a relatively high degree of refractivepower of a lens (an inverse value of a focal length) may be distributedin an object side and an image side. For example, in the optical imagingsystem, the first lens and the seventh lens may have relatively highdegrees of refractive power, while the third lens, the fourth lens, andthe fifth lens may have relatively low degrees of refractive power.

The first lens in the optical imaging system may have a surfaceincluding the most convex point of the system. In detail, theobject-side surface of the first lens includes the most convex point.The second lens in the optical imaging system may have substantially asurface including the most concave point of the system. In embodiments,an image-side surface of the second lens includes the most concavepoint.

In the optical imaging system, the third lens may have substantially arefractive index similar to that of the sixth lens. For example, incases in which the refractive index of the third lens is less than orequal to 1.55, the refractive index of the sixth lens is less than orequal to 1.55. In cases in which the refractive index of the third lensis more than or equal to 1.65, the refractive index of the sixth lens ismore than or equal to 1.65. In a manner similar to the case describedabove, in the optical imaging system the fourth lens may havesubstantially a refractive index similar to that of the seventh lens.For example, in cases in which the refractive index of the fourth lensis less than or equal to 1.55, the refractive index of the seventh lensis less than or equal to 1.55. In cases in which the refractive index ofthe fourth lens is more than or equal to 1.64, the refractive index ofthe seventh lens is more than or equal to 1.64.

A focal length of lenses forming the optical imaging system may beselected from within a predetermined range. In an example, a focallength of the first lens is selected from within a range of 2.2 mm to2.8 mm, a focal length of the second lens is selected from within arange of −7.0 mm to −3.0 mm, a focal length of the fourth lens isselected from within a range of −16 mm to −5.0 mm, and a focal length ofthe sixth lens is selected from within a range of −28 mm to −3.0 mm.

In the optical imaging system, effective diameters of lenses may bedifferent. As an example, an effective diameter of the first lens isgreater than that of the second lens. An effective diameter of thesecond lens may be greater than that of the third lens. In anembodiment, an effective diameter of the third lens is greater than orsubstantially similar to that of the fourth lens. In another example, aneffective diameter of the fifth lens is greater than that of the fourthlens and less than that of the sixth lens. An effective diameter of thesixth lens may be greater than that of the fifth lens and less than thatof the seventh lens.

In the optical imaging system, thicknesses of lenses may be different.In detail, among the first to seventh lenses, the first lens is thethickest, while the fourth lens or the fifth lens may be the thinnest.Odd-numbered lens may be substantially thicker than lenses disposedadjacently thereto. For example, the first lens is thicker than thesecond lens, while the third lens is thicker than the second lens andthe fourth lens.

Distances between lenses in the optical imaging system may be different.Distances between lenses may be gradually reduced in directions awayfrom the fourth lens and the fifth lens. For example, in the opticalimaging system, a distance between the fourth lens and the fifth lens ora distance between the fifth lens and the sixth lens are longer thanthat between other lenses. Similarly in this configuration, a distancebetween the first lens and the second lens or a distance between theseventh lens and an imaging plane is less than that between otherlenses.

Subsequently, an optical imaging system according to various exampleswill be described. First of all, the optical imaging system according toa first example will be described with reference to FIG. 1. An opticalimaging system 100 includes a first lens 110, a second lens 120, a thirdlens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, and aseventh lens 170.

The first lens 110 has a positive refractive power and opposing convexsurfaces. The second lens 120 has a negative refractive power, a convexobject-side surface, and a concave image-side surface. The third lens130 has a negative refractive power, a convex object-side surface, and aconcave image-side surface. The fourth lens 140 has a negativerefractive power, a concave object-side surface, and a convex image-sidesurface.

The fifth lens 150 has a negative refractive power, a concaveobject-side surface, and a convex image-side surface. The sixth lens 160has a negative refractive power and opposing concave surfaces. Inaddition, the sixth lens 160 includes inflection points formed onopposing surfaces. The seventh lens 170 has a positive refractive powerand opposing convex surfaces. In addition, the seventh lens 170 includesinflection points formed on opposing surfaces.

In the configuration described above, first lens 110 has the highestdegree of positive refractive power, while sixth lens 160 has thehighest degree of negative refractive power. In the example describedabove, an object-side surface of first lens 110 is more convex thansurfaces of other lenses, while the image-side surface of second lens120 is more concave than surfaces of other lenses. In the configurationdescribed above, a paraxial region of first lens 110 is formed to bethicker than paraxial regions of other lenses. A paraxial region offourth lens 140 is formed to be thinner than paraxial regions of otherlenses. In the example described above, a distance between fifth lens150 and sixth lens 160 is longer than that between other lenses. Adistance between first lens 110 and second lens 120 may be shorter thanthat between other lenses.

The optical imaging system 100 further includes a filter 180, an imagesensor 190, and a stop ST. Filter 180 is interposed between seventh lens170 and image sensor 190, while stop ST is interposed between third lens130 and fourth lens 140.

In optical imaging system 100, first lens 110 and seventh lens 170 mayhave a higher degree of refractive power than that of other lenses. In amanner different from the embodiments described above, third lens 130,fourth lens 140, and fifth lens 150 may have a lower degree ofrefractive power than that of other lenses.

A refractive index of first lens 110, a refractive index of third lens130, and a refractive index of sixth lens 160, in optical imaging system100, may be less than or equal to 1.55. In this case, the refractiveindex of first lens 110 is substantially the same as that of the thirdlens 130. The refractive index of second lens 120, the refractive indexof fourth lens 140, the refractive index of fifth lens 150, and therefractive index of seventh lens 170, in optical imaging system 100, maybe higher than or equal to 1.64. In this case, the refractive index offourth lens 140 is substantially the same as that of fifth lens 150. Inoptical imaging system 100, second lens 120 may have substantially thehighest refractive index, while first lens 110 may have substantiallythe lowest refractive index.

An effective diameter of a lens in optical imaging system 100 may begradually reduced in a direction toward stop ST. For example, aneffective diameter of third lens 130 or fourth lens 140, disposedadjacently to stop ST, may be smaller than that of lenses adjacentthereto. In a manner consistent with the case described above, a lensdisposed distantly from stop ST may have a relatively large effectivediameter. For example, seventh lens 170 disposed farthest from stop STmay has the largest effective diameter.

An optical imaging system having the configuration described above hasaberration characteristics as illustrated in the graphs of FIG. 2. FIG.3 lists aspherical characteristics of the optical imaging systemaccording to the example. Table 1 lists lens characteristics of theoptical imaging system according to the example.

TABLE 1 First Example f = 5.9976 TL = 5.195 IMG HT = 2.75 Radius ofThickness/ Focal Refractive Abbe Surface No. Curvature Distance LengthIndex Number S1 1.4300 0.7860 2.580 1.537 55.8 First Lens S2 −31.81000.1000 S3 5.2600 0.1800 −6.310 1.684 20.4 Second Lens S4 2.3000 0.3080S5 3.0300 0.2610 −20.520 1.537 55.8 Third Lens S6 2.3000 0.1210 S7 Stopinfinity 0.1960 S8 −5.4000 0.1600 −12.120 1.641 23.9 Fourth Lens S9−17.8700 0.3100 S10 −4.1600 0.1900 −13.570 1.641 23.9 Fifth Lens S11−8.1100 0.7890 S12 −4.2000 0.1640 −5.520 1.546 56.0 Sixth Lens S1310.8900 0.1080 S14 16.5500 0.7220 7.210 1.657 21.5 Seventh Lens S15−6.5300 0.1000 S16 infinity 0.1100 1.519 64.2 Imaging Filter infinity0.5900 Plate

An optical imaging system according to a second example will bedescribed with reference to FIG. 4. An optical imaging system 200includes a first lens 210, a second lens 220, a third lens 230, a fourthlens 240, a fifth lens 250, a sixth lens 260, and a seventh lens 270.

The first lens 210 has a positive refractive power and opposing convexsurfaces. The second lens 220 has a negative refractive power, a convexobject-side surface, and a concave image-side surface. The third lens230 has a negative refractive power, a convex object-side surface, and aconcave image-side surface. The fourth lens 240 has a negativerefractive power, a concave object-side surface, and a convex image-sidesurface.

The fifth lens 250 has a negative refractive power, a concaveobject-side surface, and a convex image-side surface. The sixth lens 260has a negative refractive power and opposing concave surfaces. Inaddition, the sixth lens 260 includes inflection points formed onopposing surfaces. The seventh lens 270 has a positive refractive powerand opposing convex surfaces. In addition, the seventh lens 270 includesinflection points formed on opposing surfaces.

In the configuration described above, first lens 210 has the highestdegree of positive refractive power, while sixth lens 260 has thehighest degree of negative refractive power. In the example describedabove, an object-side surface of first lens 210 is more convex thansurfaces of other lenses, while the image-side surface of third lens 230is more concave than surfaces of other lenses. In the configurationdescribed above, a paraxial region of first lens 210 is formed to bethicker than paraxial regions of other lenses. A paraxial region of thefourth lens 240 may be formed to be thinner than paraxial regions ofother lenses. In the example described above, a distance between fifthlens 250 and sixth lens 260 is longer than that between other lenses. Adistance between first lens 210 and second lens 220 may be shorter thanthat between other lenses.

The optical imaging system 200 further includes a filter 280, an imagesensor 290, and a stop ST. Filter 280 is interposed between seventh lens270 and image sensor 290, while stop ST is interposed between third lens230 and fourth lens 240.

In the optical imaging system 200, first lens 210 and seventh lens 270may have a higher degree of refractive power than that of other lenses.In a manner different from the embodiments described above, third lens230, fourth lens 240, and fifth lens 250 may have a lower degree ofrefractive power than that of other lenses.

A refractive index of first lens 210, a refractive index of third lens230, and a refractive index of sixth lens 260, in optical imaging system200, may be less than or equal to 1.55. In this case, the refractiveindex of first lens 210 is substantially the same as that of third lens230. The refractive index of second lens 220, the refractive index offourth lens 240, the refractive index of fifth lens 250, and therefractive index of seventh lens 270, in optical imaging system 200, maybe higher than or equal to 1.64. In this case, the refractive index offourth lens 240 is substantially the same as that of fifth lens 250. Inoptical imaging system 200, second lens 220 may have substantially thehighest refractive index, while first lens 210 may have substantiallythe lowest refractive index.

An effective diameter of a lens in optical imaging system 200 may begradually reduced in a direction toward stop ST. For example, aneffective diameter of fourth lens 240 disposed adjacently to stop ST issmaller than that of lenses adjacent thereto. In a manner consistentwith the embodiment described above, a lens disposed distantly from stopST may have a relatively large effective diameter. For example, seventhlens 270 disposed farthest from stop ST has the largest effectivediameter.

An optical imaging system having the configuration described aboverepresents aberration characteristics as illustrated in the graphs ofFIG. 5. FIG. 6 lists aspherical characteristics of the optical imagingsystem according to the example. Table 2 lists lens characteristics ofthe optical imaging system according to the example.

TABLE 2 Second Example f = 5.9976 TL = 5.149 IMG HT = 2.75 Radius ofThickness/ Focal Refractive Abbe Surface No. Curvature Distance LengthIndex Number S1 1.3700 0.8040 2.430 1.537 55.8 First Lens S2 −22.71000.0800 S3 5.7100 0.1500 −5.980 1.684 20.4 Second Lens S4 2.3300 0.3180S5 2.9000 0.2300 −11.950 1.537 55.8 Third Lens S6 1.9400 0.1120 S7 Stopinfinity 0.1450 S8 −7.6900 0.1500 −14.230 1.641 23.9 Fourth Lens S9−49.4100 0.2780 S10 −5.5400 0.1830 −5.670 1.641 23.9 Fifth Lens S11−12.5400 0.8500 S12 −3.7500 0.1570 −5.150 1.546 56.0 Sixth Lens S1311.4600 0.1000 S14 53.8000 0.7920 7.000 1.657 21.5 Seventh Lens S15−5.0000 0.1000 S16 infinity 0.1100 1.519 64.2 Imaging Filter infinity0.5900 Plate

An optical imaging system according to a third example will be describedwith reference to FIG. 7. An optical imaging system 300 includes a firstlens 310, a second lens 320, a third lens 330, a fourth lens 340, afifth lens 350, a sixth lens 360, and a seventh lens 370.

The first lens 310 has a positive refractive power and opposing convexsurfaces. The second lens 320 has a negative refractive power, a convexobject-side surface, and a concave image-side surface. The third lens330 has a negative refractive power, a convex object-side surface, and aconcave image-side surface. The fourth lens 340 has a negativerefractive power, a convex object-side surface, and a concave image-sidesurface.

The fifth lens 350 has a negative refractive power, a concaveobject-side surface, and a convex image-side surface. The sixth lens 360has a negative refractive power and opposing concave surfaces. Inaddition, the sixth lens 360 includes inflection points formed onopposing surfaces. The seventh lens 370 has a positive refractive powerand opposing convex surfaces. In addition, the seventh lens 370 includesinflection points formed on opposing surfaces.

In the configuration described above, first lens 310 has the highestdegree of positive refractive power, while sixth lens 360 has thehighest degree of negative refractive power. In the example describedabove, an object-side surface of first lens 310 is more convex thansurfaces of other lenses, while the image-side surface of third lens 330is more concave than surfaces of other lenses. In the configurationdescribed above, a paraxial region of first lens 310 is formed to bethicker than paraxial regions of other lenses. A paraxial region of thefifth lens 350 may be formed to be thinner than paraxial regions ofother lenses. In the example described above, a distance between fifthlens 350 and sixth lens 360 is longer than that between other lenses. Adistance between the first lens 310 and the second lens 320 and adistance between the sixth lens 360 and the seventh lens 370 may beshorter than that between other lenses.

The optical imaging system 300 further includes a filter 380, an imagesensor 390, and a stop ST. Filter 380 is interposed between seventh lens370 and image sensor 390, while stop ST is interposed between third lens330 and fourth lens 340.

In optical imaging system 300, first lens 310 and seventh lens 370 mayhave a higher degree of refractive power than that of other lenses. In amanner different from the case described above, third lens 330, fourthlens 340, and fifth lens 350 may have a lower degree of refractive powerthan that of other lenses.

A refractive index of first lens 310, a refractive index of third lens330, and a refractive index of sixth lens 360, in optical imaging system300, may be less than or equal to 1.55. In this case, the refractiveindex of first lens 310 is substantially the same as that of third lens330. The refractive index of second lens 320, the refractive index offourth lens 340, the refractive index of fifth lens 350, and therefractive index of seventh lens 370, in optical imaging system 300, maybe greater than or equal to 1.64. In this case, the refractive index offourth lens 340 is substantially the same as that of fifth lens 350. Inoptical imaging system 300, second lens 320 may have substantially thehighest refractive index, while first lens 310 may have substantiallythe lowest refractive index.

An effective diameter of a lens in optical imaging system 300 may begradually reduced in a direction toward stop ST. For example, aneffective diameter of fourth lens 340 disposed adjacently to stop ST issmaller than that of lenses adjacent thereto. Similarly based on theconfiguration described above, a lens disposed distantly from stop SThas a relatively large effective diameter. In an embodiment, seventhlens 370 disposed farthest from stop ST has the largest effectivediameter.

An optical imaging system having the configuration described aboverepresents aberration characteristics as illustrated in the graphs ofFIG. 8. FIG. 9 lists aspherical characteristics of the optical imagingsystem according to the example. Table 3 lists lens characteristics ofthe optical imaging system according to the example.

TABLE 3 Third Example f = 5.9976 TL = 5.199 IMG HT = 2.50 Radius ofThickness/ Focal Refractive Abbe Surface No. Curvature Distance LengthIndex Number S1 1.3700 0.7970 2.460 1.537 55.8 First Lens S2 −29.12000.1000 S3 Second Lens 4.3100 0.2000 −5.770 1.684 20.4 S4 2.0000 0.1650S5 3.3500 0.2630 −11.180 1.537 55.8 Third Lens S6 2.0900 0.1060 S7 Stopinfinity 0.1000 S8 10.9900 0.2000 −8.550 1.641 23.9 Fourth Lens S93.6300 0.3660 S10 −18.1200 0.1770 — 1.641 23.9 Fifth Lens 263.370 S11−20.3700 0.8750 S12 −3.4000 0.2000 −4.850 1.546 56.0 Sixth Lens S1312.3100 0.1000 S14 Seventh 15.2300 0.7000 6.300 1.657 21.5 S15 Lens−5.5800 0.1000 S16 infinity 0.1100 1.519 64.2 Imaging Filter infinity0.6400 Plate

An optical imaging system according to a fourth example will bedescribed with reference to FIG. 10. An optical imaging system 400includes a first lens 410, a second lens 420, a third lens 430, a fourthlens 440, a fifth lens 450, a sixth lens 460, and a seventh lens 470.

The first lens 410 has a positive refractive power and opposing convexsurfaces. The second lens 420 has a negative refractive power, a convexobject-side surface, and a concave image-side surface. The third lens430 has a positive refractive power, a concave object-side surface, anda convex image-side surface. The fourth lens 440 has a negativerefractive power, a convex object-side surface, and a concave image-sidesurface.

The fifth lens 450 has a positive refractive power, a concaveobject-side surface, and a convex image-side surface. The sixth lens 460has a negative refractive power, a concave object-side surface, and aconvex image-side surface. In addition, the sixth lens 460 includesinflection points formed on opposing surfaces. The seventh lens 470 hasa negative refractive power and opposing concave surfaces. In addition,the seventh lens 470 includes inflection points formed on opposingsurfaces.

In the configuration described above, first lens 410 has the highestdegree of positive refractive power, while second lens 420 has thehighest degree of negative refractive power. In the example describedabove, an object-side surface of first lens 410 is more convex thansurfaces of other lenses, while the image-side surface of second lens420 is more concave than surfaces of other lenses. In the configurationdescribed above, a paraxial region of first lens 410 is formed to bethicker than paraxial regions of other lenses. A paraxial region offifth lens 450 may be formed to be thinner than paraxial regions ofother lenses. In the example described above, a distance between fourthlens 440 and fifth lens 450 is longer than that between other lenses. Adistance between sixth lens 460 and seventh lens 470 or a distancebetween seventh lens 470 and an imaging plane may be shorter than thatbetween other lenses.

The optical imaging system 400 further includes a filter 480, an imagesensor 490, and a stop ST. Filter 480 is interposed between seventh lens470 and image sensor 490, while stop ST is interposed between secondlens 420 and third lens 430.

In optical imaging system 400, first lens 410 may have a higher degreeof refractive power than that of other lenses. In a manner differentfrom the example described above, third lens 430, fourth lens 440, andfifth lens 450 may have a relatively low degree of refractive power.

A refractive index of first lens 410, a refractive index of fourth lens440, and a refractive index of seventh lens 470, in optical imagingsystem 400, may be less than or equal to 1.55. In this case, therefractive index of first lens 410 is substantially the same as that offourth lens 440. The refractive index of second lens 420, the refractiveindex of third lens 430, the refractive index of fifth lens 450, and therefractive index of sixth lens 460, in optical imaging system 400, maybe greater than or equal to 1.65. In this case, the refractive index ofthird lens 430, the refractive index of fifth lens 450, and therefractive index of sixth lens 460 are substantially the same. Inoptical imaging system 400, second lens 420 may have substantially thehighest refractive index, while first lens 410 may have substantiallythe lowest refractive index. In optical imaging system 400, one offourth lens 440 and fifth lens 450 may have a refractive index greaterthan or equal to 1.6, and the other may have a refractive index lessthan or equal to 1.6. Fourth lens 440 and fifth lens 450, having theconfiguration described above, increase an effect of aberrationimprovement

An effective diameter of a lens in optical imaging system 400 may begradually reduced in a direction toward stop ST. For example, aneffective diameter of third lens 430 disposed adjacently to stop ST maybe smaller than that of lenses adjacent thereto. In a manner consistentwith the configuration described above, a lens disposed distantly fromstop ST may have a relatively large effective diameter. For example,seventh lens 470 disposed farthest from stop ST has the largesteffective diameter.

An optical imaging system having the configuration described aboverepresents aberration characteristics as illustrated in the graphs ofFIG. 11. FIG. 12 lists aspherical characteristics of the optical imagingsystem according to the example. Table 4 lists lens characteristics ofthe optical imaging system according to the example.

TABLE 4 Fourth Example f = 5.9976 TL = 5.296 IMG HT = 2.40 Radius ofThickness/ Focal Refractive Abbe Surface No. Curvature Distance LengthIndex Number S1 1.4800 0.8110 2.460 1.546 56.0 First Lens S2 −12.37000.1330 S3 9.2600 0.2000 −3.910 1.684 20.4 Second Lens S4 2.0200 0.2220S5 infinity 0.1000 Third Lens S6 −6.0300 0.2480 10.180 1.657 21.5 S7Stop −3.2200 0.1000 S8 19.0700 0.2000 −6.000 1.546 56.0 Fourth Lens S92.7900 0.7690 S10 −14.1900 0.1640 47.550 1.657 21.5 Fifth Lens S11−9.8000 0.5920 S12 −2.7600 0.3850 −24.760 1.657 21.5 Sixth Lens S13−3.5000 0.1000 S14 −17.6100 0.3770 −9.25 1.546 56.0 Seventh Lens S157.1500 0.1000 S16 infinity 0.1100 1.519 64.2 Imaging Filter infinity0.6850 Plate

Table 5 illustrates values of Conditional Equations of the opticalimaging system according to first to fourth examples.

TABLE 5 Conditional First Second Third Fourth Equation Example ExampleExample Example TL/f 0.8670 0.8587 0.8670 0.8837 BFL/f 0.1334 0.13340.1417 0.1493 f/(IMG HT) 2.181 2.181 2.399 2.499 Nd7 1.657 1.657 1.6571.546 f5/f −2.2628 −0.9455 −43.9127 7.9280 f/EPD 2.40 2.60 2.60 2.40

Hereinafter, a portable terminal including an optical imaging systemmounted therein, according to an example, will be described withreference to FIGS. 13 and 14. A portable terminal 10 includes aplurality of camera modules 20 and 30. A first camera module 20 includesa first optical imaging system 101 configured to capture an image of asubject at a short distance. A second camera module 30 includes secondoptical imaging systems 100, 200, 300, and 400, configured to capture animage of a distant subject.

The first optical imaging system 101 includes a plurality of lenses. Forexample, first optical imaging system 101 includes four or more lenses.First optical imaging system 101 is configured to capture images ofobjects at short distance. In detail, first optical imaging system 101has a relatively wide angle of view of 50° or more, while a ratio (TL/f)thereof may be higher than or equal to 1.0.

The second optical imaging systems 100, 200, 300, and 400 include aplurality of lenses. For example, second optical imaging systems 100,200, 300, and 400 include seven lenses. Second optical imaging systems100, 200, 300, and 400 may be provided as one optical imaging systemamong optical imaging systems according to the first to fourth examplesdescribed above. Second optical imaging systems 100, 200, 300, and 400may be configured to capture an image of a distant object. In detail,second optical imaging systems 100, 200, 300, and 400 have an angle ofview of 40° or less, while a ratio (TL/f) thereof may be below 1.0.

First optical imaging system 101 and second optical imaging systems 100,200, 300, and 400 may have substantially the same size. In someembodiments, an overall length L1 of first optical imaging system 101 issubstantially the same as an overall length L2 of second optical imagingsystems 100, 200, 300, and 400. Alternatively, a ratio (L1/L2) of theoverall length L1 of first optical imaging system 101 to the overalllength L2 of second optical imaging systems 100, 200, 300, and 400 isfrom 0.8 to 1.0. As a further alternative, a ratio (L2/h) of the overalllength L2 of second optical imaging systems 100, 200, 300, and 400 to athickness h of portable terminal 10 may be less than or equal to 0.8.

As set forth above, according to examples, an optical imaging systemcapable of capturing images of distant objects and being mounted in asmall terminal is provided. While this disclosure includes specificexamples, it will be apparent after an understanding of the disclosureof this application that various changes in form and details may be madein these examples without departing from the spirit and scope of theclaims and their equivalents. The examples described herein are to beconsidered in a descriptive sense only, and not for purposes oflimitation. Descriptions of features or aspects in each example are tobe considered as being applicable to similar features or aspects inother examples. Suitable results may be achieved if the describedtechniques are performed in a different order, and/or if components in adescribed system, architecture, device, or circuit are combined in adifferent manner, and/or replaced or supplemented by other components ortheir equivalents. Therefore, the scope of the disclosure is defined notby the detailed description, but by the claims and their equivalents,and all variations within the scope of the claims and their equivalentsare to be construed as being included in the disclosure.

What is claimed is:
 1. An optical imaging system, comprising: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens, sequentially disposed from an object side to an imaging plane, wherein the fourth lens and the fifth lens have negative refractive power, and the seventh lens has positive refractive power.
 2. The optical imaging system of claim 1, wherein the first lens has a convex image-side surface along an optical axis.
 3. The optical imaging system of claim 1, wherein the second lens has a convex object-side surface along an optical axis.
 4. The optical imaging system of claim 1, wherein the third lens has a convex object-side surface along an optical axis.
 5. The optical imaging system of claim 1, wherein the fourth lens has a meniscus form in which one side surface is concave along an optical axis, and the other side surface is convex along the optical axis.
 6. The optical imaging system of claim 1, wherein the fifth lens has a concave object-side surface along an optical axis.
 7. The optical imaging system of claim 1, wherein the sixth lens has opposing concave surfaces along an optical axis.
 8. The optical imaging system of claim 1, wherein the seventh lens has opposing convex surfaces along an optical axis.
 9. An optical imaging system, comprising: first to seventh lenses, sequentially disposed from an object side to an imaging plane, wherein a ratio (TL/f) of a distance TL from an object-side surface of the first lens to an imaging plane to an overall focal length f is lower than or equal to 1.0.
 10. The optical imaging system of claim 9, wherein the optical imaging system satisfies the following expression: BFL/f<0.15 where BFL represents a distance from an image-side surface of the seventh lens to an imaging plane.
 11. The optical imaging system of claim 9, wherein the optical imaging system satisfies the following expression: 0.1<f/(IMG HT)<2.5 where IMG HT is a half diagonal length of the imaging plane.
 12. The optical imaging system of claim 9, wherein the optical imaging system satisfies the following expression: 1.5<Nd7<1.7 where Nd7 represents a refractive index of the seventh lens.
 13. The optical imaging system of claim 9, wherein the optical imaging system satisfies the following expression: −45<f5/f<45 where f5 represents a focal length of a fifth lens.
 14. The optical imaging system of claim 9, wherein the optical imaging system satisfies the following expression: 2.0<f/EPD<2.8 where EPD represents a diameter of an entrance pupil.
 15. The optical imaging system of claim 9, wherein a second lens, a fourth lens, and a sixth lens each have a negative refractive power.
 16. The optical imaging system of claim 9, wherein a sixth lens has a concave object-side surface along an optical axis.
 17. An optical imaging system, comprising: a first lens comprising a positive refractive power, a convex object-side surface along an optical axis and a convex image-side surface along the optical axis; a second lens to sixth lens; and a seventh lens comprising a positive refractive power, a convex object-side surface along the optical axis and a convex image-side surface along the optical axis, wherein the first lens to seventh lens are sequentially disposed from an object side to an imaging plane.
 18. The optical imaging system of claim 17, wherein the object-side surface of the first lens comprises a most convex point of the optical imaging system. 